1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device including an inspection process of a semiconductor element that uses semiconductor characteristics (e.g., a transistor, in particular, a field-effect transistor; typically, a metal oxide semiconductor (MOS) transistor and a thin film transistor (TFT)). More specifically, the present invention relates to a non-contact type inspection apparatus and an inspection method using the same. The present invention also relates to a method of manufacturing a semiconductor device including an inspection process of such a semiconductor element.
2. Description of the Related Art
In an active matrix type liquid crystal display and an electroluminescence (EL) display, a TFT is generally provided in each pixel. In the case of a liquid crystal display, one TFT formed in each pixel functions as a switching element. In the case of an EL display, among a plurality of TFTs formed in each pixel, some TFTs function as switching elements, while others control a current.
It is very effective in terms of reduction in cost that an inspection process of identifying a defective product is included in an early stage in the course of manufacturing a display in which a number of TFTs are formed before a product is completed. The reasons for this are as follows: it is not required to conduct the succeeding steps with respect to a defective product; it is easy to repair a defective product due to early finding thereof, etc.
For example, in an EL display, one electrode (pixel electrode) of an EL element and a capacitor may be connected to each other with a transistor formed therebetween. It is difficult to confirm the presence of a defect until an EL display is completed and a display is actually conducted, even if there is some inconvenience in circuits or circuit elements for controlling light emission of a light-emitting element. Regarding even an EL panel that will not actually become a product, in order to be distinguished from a satisfactory product, a light-emitting element is formed, packaging is conducted, and a connector is attached to complete an EL display, whereby an inspection is conducted to the EL display. In this case, the processes of forming a light-emitting element, packaging, and attaching a connector become useless, so that time and cost cannot be reduced. Furthermore, even in the case of forming an EL panel using a multiple-chamfered substrate, the processes of packaging and attaching a connector become useless, so that time and cost cannot be also reduced.
In order to detect a portion where a malfunction is caused due to the variation in pattern width of a semiconductor film, an insulating film, or a wiring (hereinafter, merely referred to as a “pattern”) and a portion where wiring is disconnected or short-circuited due to dust or defective film formation, and to confirm if circuit or circuit elements to be inspected are operated normally, an inspection is conducted. Such a defect inspection is mainly classified into an optical inspection method and a probe inspection method.
According to the optical inspection method, a pattern formed on a substrate is read by a CCD or the like, and the read pattern is compared with a reference pattern to identify a defect. According to the probe inspection method, minute pins (probes) are put up at terminals on a substrate side, and a defect is identified based on the magnitude of a current or a voltage between the probes. In general, the former method is called a non-contact type inspection method, and the latter is called a stylus type inspection method.
A good TFT substrate that can be used for a product is discriminated from a defective TFT substrate that cannot be used for a product by the above-mentioned inspection method in which wiring is directly connected (contact) to a TFT substrate. However, according to this method, dust is likely to adhere to a substrate during attachment and removal of connection wiring. Furthermore, according to the method of detecting a defective portion by directly bringing minute pins (probes) into contact with wiring, wiring may be damaged. This inspection method may unnecessarily increase defective products during an inspection process. Also, according to the optical inspection method, a long time is required to inspect many times.